|Kristen Stewart in 'On the Road'|
The 22-year-old actress was originally planning to walk the red carpet for the film version of Jack Kerouac's classic novel on August 16 - but with her co-star Tom Sturridge, a close friend of Robert Pattinson.
A source told website RadarOnline: "Kristen won't be doing the red carpet for 'On The Road' - she's too ashamed to show her face in public right now.
"After everything that has been said, and in light of the revelations that she cheated on Robert with director Rupert Sanders, she's running scared at the moment.
The insider continued: "There's also the dilemma of standing next to her co-star in the movie, Tom Sturridge.
He's very close to Rob and Kristen thinks it would be awkward for her to promote the movie on the red carpet alongside him.
"Kristen is very proud of her work for 'On The Road', she grew up reading Kerouac novels and this is a production she always wanted to star in."
They added: "If she appears at the London premiere, it will detract people from the movie itself and Kristen doesn't want that at all.
"She wants her performance and this film to be recognised for what it is - a great adaptation of a classic book."